j1Bessel function of order one.
double x, y, j1();
y = j1(x);
Returns a Bessel function of order one of the argument.
The domain is divided into the intervals [0, 8] and (8, infinity). In the first interval a 24 term Chebyshev expansion is used. In the second, the asymptotic trigonometric representation is employed, using two rational functions of degree 5/5.
arithmetic domain # trials peak rms
DEC 0, 30 10000 4.0e-17 1.1e-17
IEEE 0, 30 30000 2.6e-16 1.1e-16